A known variable valve mechanism, as that disclosed, for example, in Japanese Patent Laid-open No. 2000-234507, varies a maximum lift amount and open/close timing of a valve according to an engine operating condition. The variable valve mechanism disclosed in Japanese Patent Laid-open No. 2000-234507 includes a variable mechanism and an actuator. The variable mechanism varies the maximum lift amount and open/close timing of a valve according to an angular position of a control shaft. The actuator controls the angular position of the control shaft. The actuator is connected to the side of a worm gear of a worm gear mechanism. The control shaft is connected to the side of a worm wheel of the worm gear mechanism. Accordingly, rotation of the actuator is inputted to the control shaft with rotational speed thereof being reduced by the worm gear mechanism.
The known variable valve mechanism cited above includes a restriction mechanism that restricts maximum angular positions of the control shaft in forward and backward rotation. The restriction mechanism includes a restriction pin that rotates integrally with the worm wheel and a restriction member fixed to an accommodation cover of the worm gear mechanism. The restriction pin abuts on the restriction member, so that the worm wheel is prevented from further rotating. The maximum angular position of the control shaft is thereby restricted. In addition, an elastic body is integrally fixed to the restriction member to absorb impact that would otherwise be received when the restriction pin contacts the restriction member.
Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention.
Japanese Patent Laid-open No. 2000-234507
Japanese Patent Laid-open No. 2002-349215